Optimization of residual stresses generated by ultrasonic nanocrystalline surface modification through analytical modeling and data-driven prediction

Abstract

In this work, we have developed a fast and robust analytical model based on the Hertzian contact theory and the Neuber's plasticity law to predict the residual stress generated by ultrasonic nanocrystal surface modification (UNSM). The measured residual stresses data for a number of different metals was used to validate the analytical model. Sensitivity studies as well as the linear regression analysis were conducted to study the effects of UNSM parameters (striking amplitude, static load, spacing, scanning speed and temperature) on the distribution of residual stresses and the surface finish. The analysis shows that a balance between residual stress and surface finish needs to be considered when choosing the UNSM parameters: the increase of ultrasonic striking amplitude and static load improve the magnitude and depth of the residual stress at the risk of deteriorating the surface finish; a higher temperature leads to a lower magnitude but deeper residual stress as well as a better surface finish; smaller tip size can significantly increase the magnitude of residual stresses but it also deteriorates the surface finish. Finally, an experimental design based on a large database (with a total of 18876 sets of UNSM parameters) was introduced to find the optimal UNSM parameters for different engineering needs.